The grey conduit exiting the trans on right side is probably going to a j box, an LB or to a sub panel, and you could get a master electrician to install a photocell on the j box or sub panel. They are not too expensive, 10-20 bucks and probably 80-120 labor to an electrician for service call and 30 minutes of their time. an outdoor digital timer box by intermatic will probably cost around 250 for labor and parts from most electricians. tork you could add 100 bucks to that. with a covered area or protected from rain or direct sunlight, I have used the smaller $20 digital timers that fit in a single gang metal outdoor outlet box and in use bubble cover, but they are not really made for outdoor use.

This is the existing system on the front main part of home. There are 4 of these trans, 2 in garage and 2 somewhere else, i didnt go look where. But all of them are controlled by switches to turn on/off lighting...I dont know if they'd be line or low voltage switches, I dont have much experiance with those.
The homeowner asked me as an afterthought if when I was finished installing the new system (rest of property) that I could install timers for those instead of having to turn on/off switches. Just wondering if possible and if thats the best way to do it or is it wise to install new transformers?
Keep in mind I am not a licensed line voltage electrician, only low voltage.
Thanks for the help...Priceless

Kind of looks like a Seagull or Kichler interior transformer. Sort of like you would use for low voltage cove lighting or monorail track. Should be simple, like David said, get a licensed electrician to wire in a timer switch in place of the existing toggle switches and you are in business.
I would be interested if it says on the transformer "for interior use only" though.

mentioned above, If you have line voltage toggle switches then it is no big deal to have an electrician install one timer per switche panel location. those decor sized timers fit in a switch panel and cost about 20 bucks at home depot or Lowes. some for a few dollars more have the ability to be astrological, but a bit harder to program.